Cross-sectional monitoring of resin impregnation using an area-sensor array in an RTM process

It is difficult to visualize the flow in the cross-section direction, and most conventional methods for monitoring resin flow are limited to the in-plane direction. This study investigates the monitoring of the cross-section of resin impregnation using an area-sensor array during a resin transfer molding (RTM) process. The area-sensor array is mounted on a thin polyimide film that is integrated with the inter-digital electrode array and associated wiring, and forms the bottom layer of the stacked composite laminates. Each area-sensor is square-shaped and measures the capacitance and electrical resistance of the sensor region. First, we constructed the equivalent electrical circuit model of in-plane and out-of-plane impregnation. Using this model, we proposed a method to identify the flow direction and the ratio of the impregnation thickness by measuring the electrical capacitance and resistance. The validity of the model was confirmed by comparison with the experimental results. To demonstrate the applicability of the proposed method, the area-sensor array was applied to monitoring the resin injection through-thickness to the glass fabric laminates. As a result, the cross-section of the impregnated area could be estimated and the estimated area provided a good match to the actual impregnated area.     

Environmental contamination and external radiation dose rates from radionuclides released from the Fukushima nuclear power plant

To evaluate the environmental contamination and contributory external exposure after the accident at the Fukushima Nuclear Power Plant (FNPP), the concentrations of artificial radionuclides in soil samples from each area were analysed by gamma spectrometry. Six artificial radionuclides ((131)I, (134)Cs, (137)Cs, (129m)Te, (95)Nb and (136)Cs) were detected in soil samples around FNPP. Calculated external effective doses from artificial radionuclide contamination in soil samples around FNPP were 1.9-2.9 μSv h(-1) (8.7-17.8 mSv y(-1)) in Fukushima city on 22 March 2011. After several months, these calculated external effective doses were 0.25-0.88 μSv h(-1) (2.2-7.6 mSv y(-1)) in Fukushima city on 29 June 2011. The present study revealed that the detected artificial radionuclides around FNPP mainly shifted to long-lived radionuclides such as radioactive caesium ((134)Cs and (137)Cs) even though current levels are decreasing gradually due to the decay of short-lived radionuclides such as (131)I, (129m)Te, (95)Nb and (136)Cs. Thus, radiation exposure potency still exists even though the national efforts are ongoing for reducing the annual exposure dose closer to 1 mSv, the public dose limit. Long-term environmental monitoring around FNPP contributes to radiation safety, with a reduction in unnecessary exposure to the residents.     

Some remarks on rheological properties of concentrated solutions of galactomannans

Rheological properties of concentrated solutions of galactomannans, locust bean gum (lb-gum) and guar gum (g-gum), were compared between samples from different manufacturers to examine the effects of prescreening for polysaccharides. The angular frequency dependence curves of the storage and loss moduli were similar in shape between lb-gum samples but were different quantitatively. This results in different values of the molecular weight between entanglements in the molten state (M_e,melt) for the lb-gums, although M_e,melt is a material constant. On the other hand, M_e,melt for g-gum samples agreed with each other. It was demonstrated that the quantitative difference in the rheological properties of lb-gum solutions was attributed to the effective lb-gum concentration in the solutions and that M_e,melt is surely a material constant even for these galactomannans. This study confirms that prescreening of samples is very important for polysaccharides to estimate M_e,melt.     

The reason for the preferential use of finger millet (Eleusine coracana) in eastern African brewing

Finger millet (Eleusine coracana) is a cereal that is widely used as an ingredient for alcoholic beverages in Eastern Africa. However, the reason for its preferred use in brewing over other types of cereal is still unknown. In this study, we aim to clarify the reason for selective use of finger millet in Eastern African brewing, through a field survey and laboratory experiments. The field survey was conducted in a rural village of Tanzania, named Bupigu. In the village, finger millet was used to prepare four types of foods: ugali (stiff porridge), uji (thin porridge), togwa (saccharified beverage) and pombe (alcoholic beverage). Among them, pombe brewing was the principal method of utilization. In addition, the survey showed that the villagers recognize that finger millet is responsible for the strong taste of pombe. Furthermore, the laboratory experiment showed that the α‐amylase activity of finger millet is higher than that of other cereals cultivated in Eastern Africa, suggesting that finger millet is a preferable ingredient for enhancing the efficiency of ethanol production. In conclusion, this study demonstrated that the high amylase activity, which led to high ethanol concentrations in the alcoholic beverages, is a preferable characteristic of the finger millet.     

Gravity-controlled condensation heat transfer of carbon dioxide (relationship between condensation condition and heat transfer)

This paper concerns the condensation of carbon dioxide and its heat transfer on a vertical surface in the subcritical region. In this region, the physical properties of carbon dioxide show significant temperature and pressure dependence. In particular, as the pressure increases and approaches the critical pressure, the difference in the properties of liquid and vapor, and surface tension approach zero. Therefore, condensate flow from natural convection decreases and the configuration of condensation may differ from that at lower pressures. In this study, the configuration of condensation is observed and at the same time, condensation heat transfer is obtained by measuring the volume of condensate. Heat transfer is discussed in connection with the configuration. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res 25(4): 214–225, 1996     

Performance analysis of a double-pass thermoelectric solar air collector

The thermoelectric (TE) solar air collector, sometimes known as the hybrid solar collector, generates both thermal and electrical energies simultaneously. A double-pass TE solar air collector has been developed and tested. The TE solar collector was composed of transparent glass, air gap, an absorber plate, thermoelectric modules and rectangular fin heat sink. The incident solar radiation heats up the absorber plate so that a temperature difference is created between the thermoelectric modules that generates a direct current. Only a small part of the absorbed solar radiation is converted to electricity, while the rest increases the temperature of the absorber plate. The ambient air flows through the heat sink located in the lower channel to gain heat. The heated air then flows to the upper channel where it receives additional heating from the absorber plate. Improvements to the thermal and overall efficiencies of the system can be achieved by the use of the double-pass collector system and TE technology. Results show that the thermal efficiency increases as the air flow rate increases. Meanwhile, the electrical power output and the conversion efficiency depend on the temperature difference between the hot and cold side of the TE modules. At a temperature difference of 22.8 °C, the unit achieved a power output of 2.13 W and the conversion efficiency of 6.17%. Therefore, the proposed TE solar collector concept is anticipated to contribute to wider applications of the TE hybrid systems due to the increased overall efficiency.     

Transient hydrogen diffusion analyses coupled with crack-tip plasticity under cyclic loading

The effect of hydrogen on the material strengths of metals is known as the hydrogen embrittlement, which affects the structural integrity of a hydrogen energy system. In the present paper, we developed a computer program for a transient hydrogen diffusion–elastoplastic coupling analysis by combining an in-house finite element program with a general purpose finite element computer program to analyze hydrogen diffusion. In this program, we use a hypothesis that the hydrogen absorbed in the metal affects the yield stress of the metal.     

Separation of oil-in-water emulsions by microbubble treatment and the effect of adding coagulant or cationic surfactant on removal efficiency

This study examined the efficiencies of microbubble (MB) treatment, MB treatment with polyaluminium chloride (PAC) as a coagulant, and MB treatment with cetyltrimethylammonium chloride (CTAC) as a cationic surfactant in the separation of emulsified oil (EO) by modified column flotation. Batch mode experiments were conducted by synthesizing emulsified palm oil (d<20 μm), and the chemical oxygen demand (COD) of the influent and effluent was measured to evaluate the treatment performance. MB treatment with PAC and MB treatment with CTAC were found to be more efficient in EO removal than the MB treatment alone. At an EO concentration of ～1,000 mg L(-1) (pH 7) and under identical treatment conditions (MB generation time: 2.5 min, flotation time: 30 min), MB treatment with PAC (50 mg L(-1)) and that with CTAC (0.5 mg L(-1)) showed equally high EO removal efficiencies of 92 and 89%, respectively. This result is of significant relevance to studies focusing on the development of economical and high-efficiency flotation systems. Furthermore, the effect of pH was investigated by varying the sample pH from 3 to 8, which showed that the EO separation efficiency of MB alone increased drastically from slightly alkaline to acidic condition.